Lenovo has announced new 7-inch and 10-inch tablets with quad-core processors and Google's latest Android 4.2 operating system, becoming one of the few companies to offer that version of the OS in tablets.

The S6000 tablet has a 10-inch screen and is being marketed as a "mobile home entertainment center" by Lenovo. The A3000 tablet with a 7-inch screen is for entry-level buyers.

The tablets will be available worldwide in the second half this year, though pricing was not immediately available. The devices are being announced at the Mobile World Congress show in Barcelona this week. Many companies are announcing their products ahead of the show, which begins Monday.

The tablets have MediaTek's MTK 8389/8125 quad-core processor running at 1.2GHz, a 5-megapixel rear camera and 0.5-megapixel front camera. Optional HSPA+ connectivity and multimedia features are available with the tablets.

Lenovo's tablets join an already flooded market of tablets with multiple operating systems. Lenovo already offers a range of Android tablets, and also Windows 8 and RT tablets as part of its IdeaPad and ThinkPad product lines.

The S6000 has a "super slim profile," Lenovo said, and a screen that can display images at a 1280-by-800-pixel resolution. It offers eight hours of battery life on Wi-Fi, weighs 560 grams and is 8.6 millimeters thin.

The A3000 packs a quad-core chip in a 7-inch tablet, similar to Google's Nexus 7. The tablet has a 1024-by-600-pixel screen and is thicker than the S6000 at 11 millimeters, but lighter at 340 grams. The tablet packs the multimedia capabilities typically found in a 10-inch device, Lenovo said.

Lenovo also announced the A1000, which has the older Android 4.1 and is powered by a dual-core processor. The tablet's unique feature is Dolby Digital audio technology in the front speakers for strong playback.

Storage capabilities for the tablets were not immediately available, but the tablets have micro-SD card slots for expandable storage.

Users can choose a service called Lenovo Mobile Access, which will provide Internet access through HSPA+ or Wi-Fi. Users have to sign up for a data plan, which can be renewed. The Lenovo Mobile Access service is already available in western European countries.